Planning unknown dive

[Nwcid]

I know the adage plan your dive and dive your plan which becomes even more true when you are tec diving. I am not tec yet and maybe this is something answered in the training. I am not looking for specific answers as I am not planing on doing this type of diving until we (dive buddy) get to that point but trying to understand better how it would work.

I know most dives are planned in the fact of the "wreck" sits at 200' so you are going to go down to the wreck, spend XX amount of time. Based on XX amount of time you have a set Deco profile.

How does it work when you want to explore a new area? Say you don't know exactly what depth you will be at or for how long? Do you just set a max depth and time then stay within that?

Here is an example of why I am asking. Right now we have a train wreck that the upper car starts at about 80 FFW (depending on water level) and the lower car sits about 112 FFW. There are rumors there are more cars that lay deeper. On air this only gives you ~ 10 min bottom time (NDL) to explore is not time to get much done. When doing a search like this obviously you can set a time limit, but what about depth when you don't know how deep you are going to be?

Again not looking for exact answers as it is not something I am planning on doing till trained, just curious. In our area we have lots of unexplored areas so trying to get an idea of how to safely "explore". Our plan is to go CCR but OC answers would be great too. Here is the information I have on the train wreck site, from my website Scuba Dive Sites - Trestle Creek

 

[PfcAJ]

A bottom gas that fits within what you anticipate your deepest depth to be, and deco gases for what you anticipate your avg depth and time to be. After a few dives at the new site, you'll be able to refine your gas choices and anticipated bottom times to produce a more exact pre-dive plan.

 

[herr2720]

Slightly off topic but I've heard the rumors as well, and sometimes I wonder if the lower cars exist or if they are so buried in silt you will never find them. With the size of the diving community and all the lines running underwater in Lake Pend Oreille and Lake Coer d'Alene I would expect someone would have already run one from the 2 upper cars to the mythical engine and other cars if they ever found them.

 

[Nwcid]

Very true, but you never know. Always fun to explore and then document. That is one of the points of my website. Cut down on rumors and post detailed information of our local sites.

I know we do have a fair group of tec minded folks but going past the second car is getting past the experience and equipment many have. So below that I am not too surprised at minimal exploration of that area.

 

[herr2720]

I always thought there was a fairly decent sized Tec community there. But alas, it's beyond my skill level to go looking so maybe they keep it secret so there is no temptation to go look for them.

 

[Nwcid]

Like I said there is or maybe was, does not seem to be a lot of active tec minded folks around right now. Or maybe I just missed them if there is. Not sure if you dive local or how active you are but we try to do some fun group dives. When I do I usually post them on, https://www.facebook.com/pages/Inland-Northwest-Divers/204751646220990 It is not as active in the winter, but many are still diving. I will be dry till March when I get done teaching classes on the weekends.

 

[nimoh]

I think the answer to your question is yes, it would be covered in your training.

Depending on your training you might do a variety of things such as:

1. making multiple dive plans and take them all with you in an underwater notebook, and then choose the best ascent strategy at the end of your dive.
2. use ratio deco to plan your ascent at the end of the dive.
3. use a computer (and a backup).

there are probably more ways to do it as well. However, in all methods it is important to make sure you have enough gas to make the ascent.

 

[Jim Lapenta]

This is one of those scenarios that could just as easily be a shallow dive. The planning process should be the same. Starting with when the decision is made to dive the site. First is to gather as much information as possible about the site itself. Then the area that you want to explore - depths (USGS maps can help here as well as dept of fish and game, etc.), features, history, and first hand information. Is this area fished? If so I bet there are some reports in local magazines. Next plan the dive with your lowest target depth and appropriate gas for that depth.

Take into consideration environmental factors that would affect the choice of gas. Low vis, cold, etc. and other risk factors that could increase narcosis might make you consider adding some helium to the mix. Once you have done this start to look at the gear you will need and any support services. Safety divers? Extra gas? Lights and so on. This sounds like you could use it as a very good exercise in expedition type planning and execution of the dive. Do the first dive to establish a baseline that you will work from.

How much deeper are you ok with doing on the second dive and what factors would affect that? That it is a train wreck (literally it seems ) I would be very aware of the possibility of jagged metal that could affect your choice of line for use on it. As well as what said metal could do to suits and flesh. I'd also plan on exploring this in small stages based on conditions. And thoroughly explore each level as much as NDL's and planned deco if any allow.

Trains are big. You could likely spend ten minutes exploring a five foot section at say from 80-85 feet, then 85 -90, and so on. Damn I wish I was closer! I'd like to be in on this. Help you guys find the strong box with the undeclared gold that dropped into the boiler opening when the thing crashed and now sits at 160 feet. Just waiting to be plucked from it's watery grave. And hidden from the gubmint dirtbags that would take it or tax it.

 

[Nwcid]

Jim great points. We have dove it a couple of times and it is a lot of fun. At our experience level now basally we profile dive out and hit the deepest point. Then we start making our way up, looking and taking pics. Staying within NDL's (on air) it feels like a rushed dive vs taking out time and really enjoying it. I know 32% Nitrox would help our NDL's at that level but not be good for deeper. The reason we have not dove it on 32% yet is lack of easy access to Nitrox (working on that). We are looking at doing AN/DP this spring.

As for searching for more I just planned on tying a line off the end of the lower car and start doing arc patterns until we find something else worth tying off to. I do have the depth maps for the lake and it gets really deep really fast. Odds of finding any really goodies is slim since it was a coal train, but you never know. But it would be a great experience to find what else might be there and be the first to document it well.

 

[Jim Lapenta]

Not knowing the area I like the idea of tying off a line and doing an arc search. Just be sure to go as slow as possible and pay attention to any unusual formations. Be careful with the line. I would not use anything lighter than #36. It's what I have on my exploration reel and on one of my spools. The spool will only hold about 50 feet of it but in 2-4 ft vis 50 feet seems like a long way when exploring. Be aware that silt, algae, etc. will often hide a razor sharp edge that could cut the line or anything else it comes into contact with. Hence the going slow. Make it a challenge. See how many rivets you can document on the surfaces, what direction are they running, and any other minute details.

I get off on that kind of stuff. I taught a wreck class and the student told me that he had been on those particular sites a half dozen times. But never saw them like he did after I had him document and sketch out the features. Gave him a whole new outlook on them and appreciation for the requirements to observe and record what he saw. We picked out minute details and saw items that I'd be willing to bet most others overlook on them. Found tie offs that at first glance looked like nothing but turned out to be solid, secure, and well placed for navigating the items.